The present invention relates to novel apparatus and a method for forming the wire reinforcing cage utilized in the manufacture of concrete pipe. In particular the invention relates to the formation of the bell-shaped or female end of the reinforcing wire cage.
Prior techniques for fabricating and forming the bell end of such cages have typically involved manually cutting the circumferential wires at the bell end of a cylindrically formed cage, bending the transverse wires to define a bell shape and then wrapping a wire circumferentially around the bent out transverse wires and welding it thereto. An improved apparatus illustrated in Nordgren, U.S. Pat. No. 3,661,186 entitled Apparatus and Process For Making Concrete Pipe Reinforcement Member, issued May 9, 1972, significantly improved upon prior techniques in its provision of an apparatus including an adjustable mandrel mechansim which expanded the transverse wires at one end of the cage. The expanded wires then formed the bell end and were wrapped with a circumferential wire which was then welded thereto.
Other prior techniques have utilized corrugated or serpentine-shaped circumferential wires at the bell end, which are adapted to be stretched into the bell-shaped end by means of an expansion mandrel. These and other prior techniques, however, are relatively slow in operation and actually require many additional manual steps to form a cage to completion. The corrugated wire construction, although desirable from some aspects, leads to too much flexibility at the bell end of a completed pipe and concrete cracking may, under some circumstances, result. Also such fabric results in the extra expense of manufacturing the wire to have a corrugated configuration and the subsequent welding of the corrugated wire to the transverse wires.